Impregnated fibers comprising preceramic resin formulations, and related composite materials and methods

ABSTRACT

A preceramic resin formulation comprising a polycarbosilane preceramic polymer, an organically modified silicon dioxide preceramic polymer, and, optionally, at least one filler. The preceramic resin formulation is formulated to exhibit a viscosity of from about 1,000 cP at about 25° C. to about 5,000 cP at a temperature of about 25° C. The at least one filler comprises first particles having an average mean diameter of less than about 1.0 μm and second particles having an average mean diameter of from about 1.5 μm to about 5 μm. Impregnated fibers comprising the preceramic resin formulation are also disclosed, as is a composite material comprising a reaction product of the polycarbosilane preceramic polymer, organically modified silicon dioxide preceramic polymer, and the at least one filler. Methods of forming a ceramic matrix composite are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/819,658, filed Nov. 21, 2017, pending, which is acontinuation-in-part of U.S. patent application Ser. No. 15/651,970,entitled “PRECERAMIC RESIN FORMULATIONS, CERAMIC MATERIALS COMPRISINGTHE PRECERAMIC RESIN FORMULATIONS, AND RELATED ARTICLES AND METHODS,”filed Jul. 17, 2017, now U.S. Pat. No. 10,731,036, issued Aug. 4, 2020,the disclosure of each of which application is incorporated herein inits entirety by this reference.

This application is also related to U.S. patent application Ser. No.16/916,374, filed Jun. 30, 2020, pending, entitled “CERAMIC MATERIALSCOMPRISING PRECERAMIC RESIN FORMULATIONS, AND RELATED ARTICLES ANDMETHODS,” the disclosure of which is incorporated herein in its entiretyby this reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Contract NumberFA8811-16-9-0002 awarded by the United States Department of Defense (AirForce) and under Contract Number W15QKN-14-9-1001 (DOTC-15-01-INIT242)awarded by the United States Department of Defense (Army). Thegovernment has certain rights in the invention.

TECHNICAL FIELD

Embodiments of the disclosure relate generally to preceramic resinformulations that are resistant to heat and exhibit a high ceramic yieldwhen ceramified. More particularly, embodiments of the disclosure relateto preceramic resin formulations that include a polycarbosilane polymer,an organically modified silicon dioxide polymer, and, optionally, atleast one filler, impregnated fibers and composite materials includingthe preceramic resin formulations, and related methods of forming thecomposite materials.

BACKGROUND

Silicon carbide (SiC) and other ceramic materials are used to producearticles having high structural and mechanical strength at a temperatureabove 1,200° C. (2,200° F.). The articles are commonly used in aerospaceand other industries needing resistance to heat. As operationtemperatures increase above 1,200° C., material options for the articlesdecrease exponentially because metal and metal alloys are not viable.While ceramic matrix composites (CMCs) and carbon-carbon (C—C) materialsare conventionally used at these temperatures, these materials areexpensive and time intensive to produce by conventional precursorimpregnation and pyrolysis, slurry infiltration, reactive meltinfiltration, or chemical vapor infiltration techniques. Processing ofthe CMCs and C—C materials requires multiple heat treatments andprocessing acts to densify the materials and provide the desiredstrength. Producing CMCs requires several infiltration cycles, whichincreases the overall cost and amount of time to fabricate the CMCs.Additionally, conventional furnaces used to produce the articles are notsufficiently large to accommodate large articles, such as those neededfor large rocket motors.

One method of forming SiC and other ceramic materials is from preceramicpolymers. However, conventional preceramic polymers, such aspolycarbosilanes, have a low viscosity (less than about 200 cP), whichlimits their practical use in the preparation of CMCs where thepreceramic polymer provides the matrix of the CMC. One commonly-usedpreceramic polymer is polycarbosilane. However, the polycarbosilane haslimited use due to its low viscosity and extensive cracking after curingat, for example, 121° C. (250° F.). Additionally, the ceramic materialsformed from conventional preceramic polymers exhibit high mass loss,extensive cracking at low temperature (less than about 121° C.), highporosity, and high shrinkage. Cracking of the ceramic material isworsened as high loading of fillers is needed, rendering the ceramicmaterial formed from the conventional preceramic polymers ineffective.Viscosity modifiers or cracking mitigation additives have been used withconventional preceramic polymers. However, with the modifiers oradditives, a low ceramic yield is observed at a temperature greater thanabout 816° C. (about 1500° F.). Polycarbosilane has also been combinedwith a polysiloxane, such as polydimethylsiloxane, to improve itsviscosity. However, the ceramic yield of the resulting ceramic materialwas unacceptably low.

Surfactants (e.g., surface active agents) have been used with epoxyresins based on a diglycidyl ether of bisphenol A. The surfactantimproves fiber strength translation and prepreg uniformity of compositepressure vessels formed from the epoxy resin.

BRIEF SUMMARY

In accordance with some embodiments described herein, a preceramic resinformulation is disclosed. The preceramic resin formulation comprises apolycarbosilane preceramic polymer and an organically modified silicondioxide preceramic polymer.

In accordance with other embodiments, a preceramic resin formulationcomprising an organically modified silicon dioxide preceramic polymerand at least one filler is disclosed. The preceramic resin formulationis formulated to exhibit a viscosity of from about 200 cP at about 25°C. to about 5,000 cP at a temperature of about 25° C.

In additional embodiments, a ceramic material comprising a reactionproduct of the polycarbosilane preceramic polymer and the organicallymodified silicon dioxide preceramic polymer is disclosed.

In accordance with other embodiments, impregnated fibers comprisingfibers and a preceramic resin formulation comprising an organicallymodified silicon dioxide preceramic polymer and at least one filler isdisclosed. The at least one filler comprises first particles having anaverage mean diameter of less than about 1.0 μm and second particleshaving an average mean diameter of from about 1.5 μm to about 5 μm.

In accordance with other embodiments, a composite material comprisingfibers and a reaction product of a polycarbosilane preceramic polymer,an organically modified silicon dioxide preceramic polymer, and at leastone filler is disclosed. The at least one filler comprises firstparticles having an average mean diameter of less than about 1.0 μm andsecond particles having an average mean diameter of from about 1.5 μm toabout 5 μm.

In further embodiments, a method of forming a preceramic resinformulation is disclosed and comprises combining the polycarbosilanepreceramic polymer, the organically modified silicon dioxide preceramicpolymer, and a crosslinking agent.

In yet other embodiments, a method of forming the ceramic material isdisclosed and comprises forming the preceramic resin formulation, curingthe preceramic resin formulation to form a cured preceramic resinformulation, and ceramifying the cured preceramic resin formulation toform the ceramic material.

In still other embodiments, a method of forming a composite material isdisclosed and comprises passing fibers through a preceramic resinformulation. The preceramic resin formulation comprises an organicallymodified silicon dioxide preceramic polymer. The fibers are impregnatedwith the preceramic resin formulation and the impregnated fibers areformed into a composite material.

In yet still other embodiments, an article is disclosed. The articlecomprises a reaction product of a polycarbosilane preceramic polymer andan organically modified silicon dioxide preceramic polymer, the articleconfigured as a component of a rocket motor or of a high temperatureaerostructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified cross-sectional view of a rocket motor includingone or more ceramic material components in accordance with embodimentsof the disclosure;

FIG. 2 is a thermogravimetric analysis (TGA) curve showing the masspercent as a function of temperature for the ceramic materials describedin Example 1;

FIG. 3 is a photograph of the ceramic materials described in Example 1;

FIG. 4 is a plot showing percent shrinkage of test specimens describedin Example 3 after a 700° F. post-cure heat treatment and after a 2,000°F. ceramic conversion;

FIG. 5 is a is a plot showing mass loss of test specimens described inExample 3 after a 700° F. post-cure heat treatment and after a 2,000° F.ceramic conversion; and

FIGS. 6 and 7 show mechanical properties of test specimens described inExample 5.

DETAILED DESCRIPTION

A composite material having a low mass loss and a high ceramic yield isdisclosed, as are methods of forming the composite material. Thecomposite material is formed from a preceramic resin formulation havinga tailorable viscosity. The composite material is formed into a ceramicmatrix composite (CMC) when heated to a temperature greater than about816° C. (greater than about 1500° F.), such as greater than about 1,200°C. or greater than about 1,649° C. The preceramic resin formulationincludes at least one silicon carbide precursor, at least one silicondioxide precursor, and, optionally, at least one filler. Byappropriately selecting viscosities of the silicon carbide precursor andthe silicon dioxide precursor and particle size and loading of thefiller, the preceramic resin formulation viscosity is tailorable for usein a wet filament winding process. After curing, the preceramic resinformulation functions as a matrix of the composite material, withfibers, such as carbon fibers, in the matrix. The composite material isformed with the carbon fibers by the wet filament winding process,enabling the composite material to be formed at a significantly lowercost (about $100,000) compared to conventional CMCs (about $1,000,000).The composite material may, optionally, be ceramified to produce theCMC. The wet filament winding process also enables the compositematerial to be produced by a semi-automated process or an automatedprocess. The composite material and CMC may be used in a wide variety ofapplications, such as in cost sensitive, high temperature applications.

The composite materials and CMCs according to embodiments of thedisclosure have a ceramic yield of greater than about 90% and a massloss of less than about 10% when cured at from about 0° C. to about 400°C. or when ceramified at about 1,200° C. or higher. Since little mass islost during cure and/or ceramification, the composite materials and CMCsretain their shape and structural functionality without using theextensive fabrication required to produce conventional CMCs. The lowmass loss corresponds to low porosity of the composite materials andCMCs, eliminating the need for infiltration cycles, which are performedin conventional CMCs and are time consuming. The wet filament windingprocess enables the composite materials and CMCs to be formed at reducedfabrication time (from about 7 days to about 10 days) compared toconventional CMC fabrication techniques (from about 30 days to about 90days or longer).

The preceramic resin formulation including at least one silicon carbideprecursor and at least one silicon dioxide precursor is disclosed. Thepreceramic resin formulation may, optionally, include at least onefiller. The silicon carbide precursor and silicon dioxide precursordiffer in viscosity, enabling a viscosity of the preceramic resinformulation to be tailored by adjusting the relative amounts of thesilicon carbide precursor and silicon dioxide precursor in thepreceramic resin formulation. The filler in the preceramic resinformulation provides heat resistance to the CMC and is selected toprovide minimal effect on the viscosity of the preceramic resinformulation. The tailorable viscosity of the preceramic resinformulation increases the extent and nature of applications in which thepreceramic resin formulation may be used. By way of example only, theviscosity of the preceramic resin formulation may be tailored so thatthe preceramic resin formulation may be used to prepare CMCs where thepreceramic resin formulation functions as the matrix of the CMC and thematrix is reinforced with the carbon fibers. The preceramic resinformulation and the carbon fibers may be cured (e.g., crosslinked) andceramified (e.g., pyrolyzed) to form a ceramic material (e.g., the CMC).The ceramic material formed from the preceramic resin formulation may beformulated to exhibit desired material properties (e.g., rheologicalproperties, mechanical properties, physical properties, chemicalproperties, thermal properties). The ceramic material exhibits a lowmass loss, a high ceramic yield, and a low porosity when ceramified at atemperature greater than about 816° C. (greater than about 1500° F.),such as greater than about 1,200° C. or greater than about 1,649° C.(about 3,000° F.). The ceramic material exhibits improved performanceproperties (e.g., strength) than each of the preceramic precursorsindividually. The tailorable viscosity of the preceramic resinformulation may be achieved without losing ceramic yield during theconversion to the ceramic material. An article formed from the ceramicmaterial also exhibits reduced or no cracking. The article may beproduced by conventional composite fabrication methods, reducing thecomplexity and cost of fabricating the article.

As used herein, the term “ceramic material” means and includes areaction product of the silicon carbide precursor and silicon dioxideprecursor following cure and ceramification of the preceramic resinformulation.

As used herein, the term “ceramic yield” means and includes a residualmass of the composite material or ceramic material remaining after cureat from about 0° C. to about 400° C. and/or ceramification of thepreceramic resin formulation at a temperature of about 1,200° C. orgreater.

As used herein, the term “composite material” means and includes areaction product of the silicon carbide precursor and silicon dioxideprecursor following cure of the preceramic resin formulation and beforeceramification.

As used herein, the term “cured preceramic resin formulation” means andincludes the preceramic resin formulation after curing and beforeceramifying.

As used herein, the term “preceramic” means and includes a polymermaterial that is converted to a ceramic material when heated to atemperature of greater than about 816° C. (greater than about 1500° F.).

As used herein, the term “preceramic resin formulation” means andincludes a formulation of the silicon carbide precursor and silicondioxide precursor before curing and ceramifying.

As used herein, the terms “comprising,” “including,” “containing,”“characterized by,” and grammatical equivalents thereof are inclusive oropen-ended terms that do not exclude additional, unrecited elements ormethod steps, but also include the more restrictive terms “consistingof” and “consisting essentially of” and grammatical equivalents thereof.

As used herein, the term “may” with respect to a material, structure,feature or method act indicates that such is contemplated for use inimplementation of an embodiment of the disclosure and such term is usedin preference to the more restrictive term “is” so as to avoid anyimplication that other, compatible materials, structures, features andmethods usable in combination therewith should or must be excluded.

As used herein, the term “configured” refers to a size, shape, materialcomposition, and arrangement of one or more of at least one structureand at least one apparatus facilitating operation of one or more of thestructure and the apparatus in a pre-determined way.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items.

As used herein, the term “substantially,” in reference to a givenparameter, property, or condition, means to a degree that one ofordinary skill in the art would understand that the given parameter,property, or condition is met with a small degree of variance, such aswithin acceptable manufacturing tolerances. By way of example, dependingon the particular parameter, property, or condition that issubstantially met, the parameter, property, or condition may be at least90.0% met, at least 95.0% met, at least 99.0% met, or even at least99.9% met.

As used herein, spatially relative terms, such as “beneath,” “below,”“lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,”“right,” and the like, may be used for ease of description to describeone element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. Unless otherwise specified,the spatially relative terms are intended to encompass differentorientations of the materials in addition to the orientation depicted inthe figures. For example, if materials in the figures are inverted,elements described as “below” or “beneath” or “under” or “on bottom of”other elements or features would then be oriented “above” or “on top of”the other elements or features. Thus, the term “below” can encompassboth an orientation of above and below, depending on the context inwhich the term is used, which will be evident to one of ordinary skillin the art. The materials may be otherwise oriented (e.g., rotated 90degrees, inverted, flipped, etc.) and the spatially relative descriptorsused herein interpreted accordingly.

As used herein, the term “about” in reference to a given parameter isinclusive of the stated value and has the meaning dictated by thecontext (e.g., it includes the degree of error associated withmeasurement of the given parameter).

The following description provides specific details, such as materials,material thicknesses, and processing conditions in order to provide athorough description of embodiments of the disclosure. However, a personof ordinary skill in the art will understand that the embodiments of thedisclosure may be practiced without employing these specific details.Indeed, the embodiments of the disclosure may be practiced inconjunction with conventional fabrication techniques employed in theindustry. In addition, the description provided below does not form acomplete process flow for manufacturing the article from the preceramicresin formulation. Only those process acts and structures necessary tounderstand the embodiments of the disclosure are described in detailbelow. Additional acts to form the article from the preceramic resinformulation may be performed by conventional techniques. Also note, anydrawings accompanying the application are for illustrative purposesonly, and are thus not drawn to scale. Additionally, elements commonbetween figures may retain the same numerical designation.

The silicon carbide precursor and silicon dioxide precursor may differin viscosity from one another by at least one order of magnitude. Thesilicon carbide precursor may, for example, have a viscosity of lessthan or equal to about 250 cP at a temperature of about 25° C. while thesilicon dioxide precursor may have a viscosity of greater than or equalto about 2,500 cP at a temperature of about 25° C. While embodimentsherein describe the silicon carbide precursor as having a lowerviscosity than the silicon dioxide precursor, the silicon carbideprecursor may have a higher viscosity than the silicon dioxide precursoras long as the viscosities of the two preceramic precursors differ by atleast one order of magnitude. By selecting the viscosities of each ofthe silicon carbide precursor and silicon dioxide precursor, theviscosity of the preceramic resin formulation may be tailored asdesired.

The silicon carbide precursor is a polycarbosilane preceramic polymerformed of monomers having the following chemical structure:

where R₁ and R₂ of each monomer is independently a hydrogen (H) group, amethyl (CH₃) group, or a vinyl group (CH₂═CH) and n is an integer from 2to 10,000 (e.g., from 100 to 5,000). When vinyl groups are present, thevinyl group may be directly bonded to the silicon atom or may be bondedto the silicon atom by an alkyl group or other linker. By way of exampleonly, the alkyl group may include from one carbon atom to six carbonatoms. At least a portion of the monomers in the polycarbosilanepreceramic polymer include the vinyl group as R₁ or R₂ to enablecrosslinking with the organically modified silicon dioxide preceramicpolymer during cure of the preceramic resin formulation. The amount ofvinyl groups in the polycarbosilane preceramic polymer may be sufficientto crosslink the preceramic resin formulation. The polycarbosilanepreceramic polymer may include at least about 0.01 vinyl eq/kg, such asfrom about 0.2 vinyl eq/kg to about 5.0 vinyl eq/kg. The polycarbosilanepreceramic polymer may also include at least about 0.01 hydride eq/kg,such as from about 0.2 hydride eq/kg to about 10 hydride eq/kg. Thepolycarbosilane preceramic polymer may be photocurable, chemicallycurable, or thermally curable.

By selecting the R₁ and R₂ groups of each monomer and the degree ofpolymerization (i.e., the number of monomer repeat units), a desiredviscosity of the polycarbosilane preceramic polymer may be achieved. Thepolycarbosilane preceramic polymer is formulated to exhibit a viscosityof less than or equal to about 250 cP at a temperature of about 25° C.,such as from about 1 cP to about 250 cP at about 25° C., from about 1 cPto about 200 cP at about 25° C., from about 1 cP to about 100 cP atabout 25° C., from about 10 cP to about 250 cP at about 25° C., fromabout 10 cP to about 200 cP at about 25° C., from about 40 cP to about250 cP at about 25° C., from about 40 cP to about 200 cP at about 25°C., from about 40 cP to about 120 cP at about 25° C., from about 40 cPto about 100 cP at about 25° C., from about 5 cP to 8 cP at about 25°C., from about 4 cP to about 7 cP at about 25° C., from about 8 cP toabout 12 cP at about 25° C., from about 8 cP to about 15 cP at about 25°C., or from about 200 cP to about 250 cP at about 25° C. In someembodiments, the polycarbosilane preceramic polymer has a viscosity offrom about 40 cP to about 120 cP at about 25° C.

Such polycarbosilane preceramic polymers are commercially available fromnumerous sources including, but not limited to, EEMS, LLC (SaratogaSprings, N.Y.), Starfire Systems, Inc. (Schenectady, N.Y.), or Matech(Westlake Village, Calif.). The polycarbosilane preceramic polymer mayinclude, but is not limited to, SMP-10, STARPCS® SMP-500, or STARPCS®SMP-877 silicon carbide precursor from Starfire Systems, Inc. (Malta,N.Y.). Additional polycarbosilane preceramic polymers are commerciallyavailable from EEMS, LLC as MS 208, MS 272, MS 250, MS 440, CSO 110, orCSO 116. The polycarbosilane preceramic polymer may also include acombination of polycarbosilane preceramic polymers or a combination ofthe polycarbosilane preceramic polymer with at least one other polymer,such as a polysiloxane or other compatible polymer. The polycarbosilanepreceramic polymer may be available at a relatively low cost, such asless than about $100/pound. Commercially available polycarbosilanepreceramic polymers may also include a combination of thepolycarbosilane preceramic polymer.

The silicon dioxide precursor is an organically modified silicon dioxidepreceramic polymer formed of monomers having the following chemicalstructure:

where each of R₃ and R₄ is independently a methyl (CH₃) group or a vinylgroup (CH₂═CH) and n is an integer from 2 to 10,000 (e.g., from 100 to5,000). When vinyl groups are present, the vinyl group may be directlybonded to the silicon atom or may be bonded to the silicon atom by analkyl group or other linker. By way of example only, the alkyl group mayinclude from one carbon atom to six carbon atoms. The organicallymodified silicon dioxide preceramic polymer includes a quaternarycoordinated (QC) oxygen to silicon atom and may also be referred to as aQC silicon dioxide preceramic polymer. At least a portion of themonomers in the organically modified silicon dioxide preceramic polymermay, optionally, include the vinyl group as R₃ or R₄ to enablecrosslinking with the polycarbosilane preceramic polymer during cure ofthe preceramic resin formulation. The organically modified silicondioxide preceramic polymer may include from about 0 vinyl eq/kg to about5.0 vinyl eq/kg, such as from about 0.18 vinyl eq/kg to about 0.3 vinyleq/kg. The organically modified silicon dioxide preceramic polymer maybe photocurable, chemically curable, or thermally curable.

R₃ and R₄ of each monomer of the organically modified silicon dioxidepreceramic polymer and the degree of polymerization are selected toprovide the desired viscosity to the organically modified silicondioxide preceramic polymer. The organically modified silicon dioxidepreceramic polymer also has a low carbon content and a high degree ofquaternary coordinated oxygen to the silicon atoms in the polymer chain.The organically modified silicon dioxide preceramic polymer isformulated to exhibit a viscosity greater than about 200 cP at atemperature of about 25° C., such as greater than about 2,500 cP at atemperature of about 25° C., from about 3,000 cP to about 100,000 cP atabout 25° C., from about 4,000 cP to about 100,000 cP at about 25° C.,from about 5,000 cP to about 100,000 cP at about 25° C., from about6,000 cP to about 100,000 cP at about 25° C., from about 4,500 cP toabout 7,000 cP at about 25° C., from about 40,000 cP to about 80,000 cPat about 25° C., from about 45,000 cP to about 75,000 cP at about 25°C., from about 50,000 cP to about 70,000 cP at about 25° C., or fromabout 50,000 cP to about 60,000 cP at about 25° C. In some embodiments,the organically modified silicon dioxide preceramic polymer has aviscosity of from about 50,000 cP to about 60,000 cP at a temperature ofabout 25° C. In other embodiments, the organically modified silicondioxide preceramic polymer has a viscosity of from about 4,500 cP toabout 7,000 cP at about 25° C.

Such organically modified silicon dioxide preceramic polymers arecommercially available from numerous sources including, but not limitedto, Gelest, Inc. (Morrisville, Pa.). The organically modified silicondioxide preceramic polymer may include, but is not limited to, VQM 135,VQM 135R, VQM 146, or combinations thereof.

The preceramic resin formulation also includes a crosslinking agent,such as a radical initiator, a cationic initiator, or a hydrosilylationcatalyst. The crosslinking agent initiates crosslinking of thepolycarbosilane preceramic polymer and organically modified silicondioxide preceramic polymer by reacting the vinyl groups withsilicon-hydrogen groups in the preceramic resin formulation. The radicalinitiator may be a peroxide compound or an azo compound used to cure(e.g., crosslink) the polycarbosilane preceramic polymer and theorganically modified silicon dioxide preceramic polymer. The peroxidecompound may include, but is not limited to, benzoyl peroxide, dicumylperoxide, bis-(2,4-dichlorobenzoyl)-peroxide, or combinations thereof.The azo compound may include, but is not limited to,azobisisobutyronitrile. The cationic initiator may include a protonicacid, a Lewis acid/Friedel-Crafts catalyst (e.g., SnCl₄, AlCl₃, BF₃, andTiCl₄), carbenium ion salts (e.g., with trityl or tropylium cations), orthrough ionizing radiation. The hydrosilylation catalyst may be atransition metal catalyst, such as platinum, rhodium, ruthenium iridium,palladium, nickel, cobalt, iron, manganese, or combinations thereof. Insome embodiments, the crosslinking agent is a platinum catalyst. Thecrosslinking agent may be present at an amount sufficient to react(e.g., crosslink) the polycarbosilane preceramic polymer and organicallymodified silicon dioxide preceramic polymer and at least partiallydepends on the polycarbosilane preceramic polymer and organicallymodified silicon dioxide preceramic polymer used, as well as on thedesired cure time of the preceramic resin formulation. The crosslinkingagent may, for example, be present in the preceramic resin formulationat from about 0.01 parts per hundred parts of resin (phr) to about 2.5phr, such as from about 0.5 phr to about 2.0 phr, or about 1.0 phr.

The preceramic resin formulation may include optional components (e.g.,additives) to provide desirable properties to the ceramic materialformed from the preceramic resin formulation. If present, the additivemay be at least one compound that enhances at least one materialproperty (e.g., ceramic yield, extent of cracking) of the ceramicmaterial to be formed from the preceramic resin formulation. By way ofexample only, the additive may be a cure accelerator, an adhesionpromoter, a lubricant, a filler, a pigment, or combinations thereof.Such additives are known in the art and are not described in detailherein. In some embodiments, the preceramic resin formulation issubstantially free of additives other than the crosslinking agent. Thus,the preceramic resin formulation consists essentially of or consists ofthe polycarbosilane preceramic polymer, organically modified silicondioxide preceramic polymer, and the crosslinking agent.

The filler in the preceramic resin formulation may be a material that isresistant to temperatures to which the composite material or CMC isexposed during use and operation. The filler may have a melting point ofbetween about 1,800° C. and about 4,000° C., such as between about2,000° C. and about 3,900° C. The filler is also thermally stable at atemperature above about 1,649° C. (about 3,000° F.). The filler does notdegrade at processing temperatures and, therefore, improves the ceramicyield. The filler also exhibits a low density, minimizing the overallmass of the CMC. The density of the filler may be between 1.8 g/ml and13.0 g/ml, such as between about 2.0 g/ml and about 12.5 g/ml, orbetween about 2.1 g/ml and about 12.2 g/ml. The filler also exhibits alow effect on the viscosity of the preceramic resin formulation, even athigh filler loading. The filler may include, but is not limited to,silicon carbide, hafnium carbide, tantalum carbide, niobium carbide,zirconium carbide, tungsten carbide, molybdenum carbide, zirconiumoxide, aluminum oxide, hafnium oxide, magnesium oxide, thorium oxide,boron nitride, hafnium nitride, tantalum nitride, zirconium nitride,titanium nitride, titanium diboride, hafnium diboride, tantalumdiboride, zirconium diboride, tungsten boride, or combinations thereof.The filler is commercially available from various sources, such asMomentive Performance Materials Inc. (Waterford, N.Y.) or Panadyne Inc.(Montgomeryville, Pa.). In some embodiments, the filler is zirconiumoxide and titanium diboride.

The filler, when present, may be selected to enable a high fillerloading and high ceramic yield while having a minimal effect on thepreceramic resin formulation viscosity, a minimal effect on mechanicalproperties, and a minimal mass loss of the CMC. Generally, as the amountof filler in the preceramic resin formulation increases, the viscosityof the preceramic resin formulation increases and mechanical propertydegradation is observed. Therefore, the amount of filler in thepreceramic resin formulation is a balance between high loading and theviscosity of the preceramic resin formulation. The filler may be presentin the preceramic resin formulation at up to 65% by weight (wt %) withrespect to the resin, such as from about 1 wt % to about 65 wt %, fromabout 1 wt % to about 35 wt %, from about 5 wt % to about 30 wt %, fromabout 10 wt % to about 25 wt %, from about 15 wt % to about 20 wt %,from about 35 wt % to about 65 wt %, from about 40 wt % to about 60 wt%, from about 45 wt % to about 55 wt %, from about 45 wt % to about 65wt %, or from about 50 wt % to about 65 wt %. At a low filler loading,the CMC formed from the preceramic resin formulation may be more porousthan that formed from a preceramic resin formulation having a higherfiller loading. Therefore, if a porous CMC is desired, a low amount offiller may be present in the preceramic resin formulation. However, if anonporous CMC is desired, a higher amount of the filler may be used.Without being bound to any theory, it is believed that having at least10 wt % of the filler in the preceramic resin formulation minimizes massloss of the composite material or CMC following ceramification.

Particle size of the filler may also affect the viscosity and fillerloading of the preceramic resin formulation. To achieve a desiredbalance between the viscosity and filler loading, the filler may have anaverage mean diameter of less than or equal to the average mean diameterof filaments of the carbon fibers present in the composite material orCMC. By way of example only, if the carbon fibers include a carbon fibertow, the filler may have an average mean diameter of less than or equalto the average mean diameter of a filament of the carbon fiber tow. Theaverage mean diameter of the filler may be sufficiently small so as notto displace the carbon fibers in the composite material or CMC. Theaverage mean diameter of the filler may be appropriately selected forpositioning of the filler between individual carbon fibers and forpositioning in spaces between tows or layers of the carbon fibers. Thefiller may have an average mean diameter of from about 0.1 μm to about150 μm, such as from about 0.1 μm to about 50 μm, from about 0.1 μm toabout 40 μm, from about 0.1 μm to about 30 μm, from about 0.1 μm toabout 20 μm, from about 0.1 μm to about 10 μm, from about 0.1 μm toabout 5 μm, from about 0.5 μm to about 40 μm, from about 0.5 μm to about30 μm, from about 0.5 μm to about 20 μm, from about 0.5 μm to about 10μm, from about 0.5 μm to about 5 μm, from about 0.5 μm to about 1 μm,from about 1 μm to about 50 μm, from about 1 μm to about 40 μm, fromabout 1 μm to about 30 μm, from about 1 μm to about 20 μm, from about 1μm to about 10 μm, from about 2 μm to about 8 μm, or from about 2 μm toabout 5 μm.

The filler may be present in two or more particle sizes or particle sizeranges, where the particle sizes are selected to improve packingefficiency and loading of the filler in the preceramic resinformulation. For instance, a small particle size filler may have anaverage mean diameter of less than about 1.0 μm and a large particlesize filler may have an average mean diameter of from about 1.5 μm toabout 5 μm. The small particle size filler may be located betweenindividual carbon fiber filaments of the composite material or CMC, suchas in interfilament spaces between the carbon fiber filaments. The largeparticle size filler may be located in spaces between tows or layers ofthe carbon fibers of the composite material or CMC, such as ininter-composite ply spaces. In some embodiments, the small particle sizefiller has an average mean diameter of from about 0.5 μm to about 0.6 μmand the large particle size filler has an average mean diameter of fromabout 2 μm to about 5 μm. The filler may also include two or morefillers, with each filler having a different particle size or particlesize range. If, for example, two fillers are used, the two fillers maybe present at a ratio of 1:1, 1:2, 1:3, 1:4, 2:1, 3:1, or 4:1. In someembodiments, the two fillers are present at a ratio of 2:1.

The particle size of the filler may also affect the viscosity and fillerloading of the preceramic resin formulation. The amount of smallparticle size filler present in the preceramic resin formulation may belimited by the effect on viscosity, which increases at higher fillerloading. Using the large particle size filler may enable a higher fillerloading with a smaller effect on the viscosity of the preceramic resinformulation. By using the different particle size fillers, a desiredamount of filler may be present in the preceramic resin formulationwithout negatively affecting its viscosity.

In some embodiments, zirconium oxide and titanium diboride are presentin the preceramic resin formulation. The zirconium oxide is present atan average mean diameter of about 0.6 μm and the titanium diboride ispresent at an average mean diameter of about 3 μm and the ratio ofzirconium oxide:titanium diboride is 2:1. The zirconium oxide andtitanium diboride are present at 65 wt % with respect to the resin.

Boron nitride may, optionally, be present in the preceramic resinformulation as an additive to improve mechanical properties of the CMC.The boron nitride may improve the carbon fiber/matrix interface,enabling slippage between the carbon fibers and the matrix of the CMC.

The preceramic resin formulation may include from about 10% by weight(wt %) to about 90 wt % of the polycarbosilane preceramic polymer andfrom about 10 wt % to about 90 wt % of the organically modified silicondioxide preceramic polymer. The amount of each of the polycarbosilanepreceramic polymer and the organically modified silicon dioxidepreceramic polymer present in the preceramic resin formulation may beselected depending on the desired properties of the composite materialor ceramic material to be formed. In some embodiments, the preceramicresin formulation includes 80 wt % of the polycarbosilane preceramicpolymer, 20 wt % of the organically modified silicon dioxide preceramicpolymer, the filler at about 65 wt % of the resin, and about 1.0 phr ofthe crosslinking agent. By way of example only, the polycarbosilanepreceramic polymer is CSO-110 from EEMS, LLC and is present at about 100parts, the organically modified silicon dioxide preceramic polymer isVQM-146 from Gelest, Inc. and is present at about 25 parts, 65 wt % ofthe filler is present with respect to the resins, and the crosslinkingagent is a platinum catalyst (EEMS CLC-PL005) and is present at about 1part.

While preceramic resin formulations including polysiloxanes and apolycarbosilane preceramic polymer have been previously used, thecomposite materials or CMCs resulting from these preceramic polymers hada low ceramic yield. It was surprising and unexpected for the preceramicresin formulation including the polycarbosilane preceramic polymer, theorganically modified silicon dioxide preceramic polymer, and the fillerto produce composite materials or CMCs having a high ceramic yield.Therefore, by using the polycarbosilane and the organically modifiedsilicon dioxide preceramic polymers, the ceramic yield may be maximized.

The preceramic resin formulation may be formed by mixing thepolycarbosilane preceramic polymer, the organically modified silicondioxide preceramic polymer, the filler, and the crosslinking agent,along with any optional additives. The polycarbosilane preceramicpolymer, organically modified silicon dioxide preceramic polymer,filler, and crosslinking agent may be mixed by conventional techniques,such as by hand, using a high shear mixer, or using a planetary mixer.Mixing the components under vacuum may remove gases from the preceramicresin formulation, which inhibits the formation of voids or pores duringcuring and during the conversion of the preceramic resin formulation tothe ceramic material. The components may be mixed under inertconditions, such as under argon. The polycarbosilane preceramic polymer,organically modified silicon dioxide preceramic polymer, filler, andcrosslinking agent may be mixed for an amount of time sufficient to forma substantially homogeneous preceramic resin formulation (e.g., thepolycarbosilane preceramic polymer, organically modified silicon dioxidepreceramic polymer, filler, and crosslinking agent may be uniformlydispersed throughout the preceramic resin formulation), or may beheterogeneous (e.g., at least one of the polycarbosilane preceramicpolymer, organically modified silicon dioxide preceramic polymer,filler, and crosslinking agent may be non-uniformly dispersed throughoutthe preceramic resin formulation). In some embodiments, the preceramicresin formulation is substantially homogeneous as formed. Organicsolvents may, optionally, be used to form the preceramic resinformulation. During mixing, the preceramic resin formulation may bemaintained at a temperature below the lowest cure temperature of each ofthe components. In one embodiment, the polycarbosilane preceramicpolymer, organically modified silicon dioxide preceramic polymer,filler, and crosslinking agent are maintained at room temperature (fromabout 20° C. to about 25° C.) during mixing. A water-cooled jacket maybe used, as needed, to maintain the preceramic resin formulation at ornear room temperature to inhibit potential reactions from occurringduring the mixing.

The preceramic resin formulation exhibits a viscosity within a range offrom about 200 cP at about 25° C. to about 5,500 cP at a temperature ofabout 25° C., such as from about 800 cP at about 25° C. to about 5,000cP at a temperature of about 25° C. or from about 1,000 cP at about 25°C. to about 5,000 cP at a temperature of about 25° C. The preceramicresin formulation also exhibits a room temperature pot life.

The carbon fibers may include, but are not limited to, polyacrylonitrile(PAN) fibers or pitch fibers and may be in tow form or fabric form. Thecarbon fibers of the CMC may be compatible with the components (e.g.,ingredients) of the preceramic resin formulation. The carbon fibers mayinclude a sizing coating or may be used without a sizing coating. Thecarbon fibers may additionally be coated, such as with a boron nitridecoating, to enable slippage of the carbon fibers during loading.Suitable carbon fibers are commercially available from various sources,such as HExTow® IMT-R-12K from Hexcel Corp. (Stamford, Conn.) orgraphite fiber YSH60A-A2S-12K from Nippon Graphite Fiber Corp. (Hyogo,Japan). Since carbon fibers cost between $40 per pound and $200 perpound, compared to between $1,000 per pound and $5,000 per pound forceramic fibers, the cost of the composite material or CMC is decreasedcompared to a CMC that includes ceramic fibers. In some embodiments, thecarbon fibers are pitch fibers, which provide better thermal propertiesand higher strength under oxidative environments.

While embodiments of the composite material or CMC described hereininclude the carbon fibers, other fibers, such as ceramic fibers (SiC),glass fibers (E-glass, S2 glass), aramid fibers (e.g., KEVLAR®),polyethylene fibers (e.g., SPECTRA®), coated carbon fibers (BN coatedcarbon fibers, BN/SiC coated carbon fibers), carbon fibers with asurface converted to SiC, or combinations thereof, may be used dependingon the intended use of the CMC and its cost sensitivity. By way ofexample only, CMCs used in turbine components have a functional life ofgreater than about 10,000 hours and need to withstand thermal cyclingwith little decrease in mechanical properties. In these CMCs, ceramicfibers may be used instead of the carbon fibers. For applications havingshorter functional lives (e.g., less than about 30 minutes), such as inrocket motor nozzles, the carbon fibers may be used.

The preceramic resin formulation and carbon fibers are formed into adesired shape by coating, casting into a mold, dispensing from acontainer onto a surface as an adhesive or sealant, hand placement (layup), molding, such as vacuum bag molding or resin transfer molding,filament winding, such as wet filament winding, another suitableprocess, or combinations thereof In some embodiments, the preceramicresin formulation and carbon fibers are formed into the compositematerial or CMC by a wet filament winding process. To form the compositematerial or CMC, the carbon fibers are impregnated with the preceramicresin formulation. The carbon fibers may be passed through (e.g., dippedor otherwise immersed) in a bath containing the preceramic resinformulation. Since the preceramic resin formulation is viscous, thepreceramic resin formulation may impregnate into the carbon fibers,wetting the carbon fibers. The carbon fibers may, alternatively, becoated with the preceramic resin formulation, such as by brushing orotherwise applying the preceramic resin formulation to the carbonfibers. Once cured and ceramified, the preceramic resin formulationfunctions as the matrix of the composite material or CMC, with thecarbon fibers embedded in the matrix.

The preceramic resin formulation and carbon fibers are used at a rangeof from about 15 volume percent of the preceramic resinformulation:about 85 volume percent of the carbon fibers to about 85volume percent of the preceramic resin formulation:about 15 volumepercent of the carbon fibers, such as about 15 volume percent of thepreceramic resin formulation:about 85 volume percent of the carbonfibers, about 25 volume percent of the preceramic resinformulation:about 75 volume percent of the carbon fibers, about 35volume percent of the preceramic resin formulation:about 65 volumepercent of the carbon fibers, about 40 volume percent of the preceramicresin formulation:about 60 volume percent of the carbon fibers, or about80 volume percent of the preceramic resin formulation:about 20 volumepercent of the carbon fibers.

The impregnated carbon fibers may be formed (e.g., fabricated) into adesired configuration or shape of the composite material or CMCdepending on the intended use of the composite material or CMC. By wayof example only, the impregnated carbon fibers may be directly formedinto a desired shape by coating, casting into a mold, dispensing from acontainer onto a surface as an adhesive or sealant, hand placement (layup), molding, such as vacuum bag molding or resin transfer molding,filament winding, such as wet filament winding, another suitableprocess, or combinations thereof. Once formed into the desired shape,the carbon fibers impregnated with the preceramic resin formulation arecured (e.g., crosslinked) to form the composite material as a rigidsolid and, optionally, ceramified (e.g., pyrolyzed) to form the ceramicmaterial (e.g., CMC). The composite material may exhibit sufficientstrength and mechanical properties after curing that ceramification isoptional. The composite material or CMC is, therefore, directly formedinto a net shape or near-net shape in that the carbon fibers impregnatedwith the preceramic resin formulation are formed into the desired shapeby the wet winding process and not into a tape or other configurationthat is subsequently formed in the desired shape.

The impregnated carbon fibers may be exposed to one or more heattreatments to cure the resin matrix and form the composite material as arigid solid. The composite material may, optionally, be ceramified toform the CMC. The conditions used to cure the impregnated carbon fibersmay be selected depending on the specific polycarbosilane preceramicpolymer and organically modified silicon dioxide preceramic polymerpresent in the preceramic resin formulation. The cure temperature of theimpregnated carbon fibers may range from about 0° C. (about 32° F.) toabout 400° C. (about 752° F.), such as from about 20° C. to about 371°C. (700° F.), from about 121° C. (about 250° F.) to about 371° C. (700°F.), or from about 20° C. to about 121° C. (about 250° F.). Depending onthe cure temperature, the impregnated carbon fibers may be cured in anamount of time ranging from a few seconds (e.g., photoinitiated cure) toa few days. The impregnated carbon fibers may be cured in hours, such asfrom about one hour to about thirty hours, from about four hours toabout twenty hours, or from about six hours to about ten hours. Byincreasing the cure temperature, a shorter amount of time may be neededto cure the impregnated carbon fibers. Conversely, by decreasing thecure temperature, a longer amount of time may be needed to cure theimpregnated carbon fibers. The curing of the impregnated carbon fibersmay be conducted using conventional processing equipment, which is notdescribed in detail herein. During curing, the polycarbosilanepreceramic polymer and organically modified silicon dioxide preceramicpolymer in the preceramic resin formulation react (e.g., crosslink),forming a hardened composite material. Thus, the composite materialincludes a reaction product of the polycarbosilane preceramic polymerand the organically modified silicon dioxide preceramic polymer. By wayof example only, the vinyl groups of the preceramic resin formulationreact with silicon-hydrogen bonds during the cure. The curing and highertemperature heat treatments (e.g., ceramifying) may be conducted in alow oxygen environment (e.g., an inert atmosphere environment), such asbelow 100 ppm of oxygen, to reduce oxidation of the carbon fibers.

If multiple heat treatments are conducted, a first heat treatment may beconducted on the impregnated carbon fibers to initially cure thepreceramic precursors of the preceramic resin formulation. After thefirst heat treatment, the composite material may be machineable. Anymachining acts, such as adjusting an outer diameter, to produce thecomposite material in its desired shape may, therefore, be conductedfollowing the first heat treatment. A second heat treatment may then beconducted to further cure the composite material. By way of exampleonly, the first heat treatment may be conducted at a temperature of 250°F. for four hours, followed by the second heat treatment at 700° F. fortwo hours.

The composite material is ceramified to further harden the compositematerial and convert the composite material into the ceramic material(e.g., the CMC). Thus, the ceramic material includes a reaction productof the polycarbosilane preceramic polymer and the organically modifiedsilicon dioxide preceramic polymer. Without being bound by any theory,it is believe that during the cure and ceramification, the preceramicresin formulation is converted into an amorphous silicon-oxy-carbidematerial with the carbon fibers dispersed therein. The compositematerial may be exposed to a temperature of greater than about 649° C.(greater than about 1,200° F.), such as a temperature of greater thanabout 816° C. (greater than about 1,500° F.) or greater than about1,093° C. (greater than about 2,000° F.) to ceramify the compositematerial. By way of example only, the ceramification temperature mayrange from about 816° C. to about 1,093° C. or from about 816° C. toabout 1,200° C. or greater. The ceramic yield of the ceramic material orthe CMC may be greater than about 50%, such as greater than about 70%,greater than about 75%, greater than about 80%, greater than about 90%,or greater than about 95% when ceramified at these temperatures. Withoutbeing bound by any theory, it is believed that the high degree ofquaternary coordinate oxygen in the organically modified silicon dioxidepreceramic polymer results in the high ceramic yield. When silicon atomsare fully coordinated with oxygen atoms, SiO₂ is maintained during thecure and ceramification. The organically modified silicon dioxidepreceramic polymer has sufficient organic groups bonded to the siliconatoms to keep the preceramic resin formulation in a polymeric state,which enables ease of blending with other materials. It is also believedthat at a temperature of about 1,093° C. (about 2,000° F.), thepreceramic resin formulation may be characterized as a semi-amorphoussilicon-oxy-carbide material.

By forming the composite material or CMC by the wet winding process, thecomposite material or CMC may be formed into a net-shape or near-netshape. The impregnated fibers do not need to be formed into a tape orother form, which is then formed into the desired shape. Rather, thecomposite material or CMC is directly formed from the impregnatedfibers. The composite material may also be machineable during a portionof its fabrication, such as machining its outer diameter after theinitial curing stage.

For comparison, while preceramic resin formulations includingpolysiloxanes and a polycarbosilane preceramic polymer have previouslybeen formed, CMCs resulting from such preceramic resin formulations hada low ceramic yield due to the high carbon and oxygen content in thematrix. It was surprising and unexpected to find out that the preceramicresin formulations according to embodiments of the disclosure exhibiteda high ceramic yield and a low mass loss, which is believed to be due tothe high degree of quaternary coordinated oxygen to the silicon atoms inthe polymer chain.

In some embodiments, the impregnated carbon fibers are cured at atemperature of about 121° C. (about 250° F.), subjected to an additionalheat treatment at 371° C. (700° F.), and ceramified at a temperature ofabout 1,093° C. (2,000° F.). In other embodiments, the impregnatedcarbon fibers are cured and ceramified by a single heat treatment, suchas a temperature of about 1,200° C.

In embodiments where the CMC was cured at about 121° C. (about 250° F.)for about four hours, at about 371° C. (about 700° F.) for about twohours, and ceramic conversion at about 1,093° C. (about 2,000° F.) forabout 30 minutes, the CMC exhibited low mass loss and a low change indimensions (e.g., shrinkage). The CMC exhibited less than about 5%shrinkage. In other embodiments, the CMCs were cured using a single heattreatment at 1,200° C. and by a semi-automated process, reducing costand fabrication time compared to conventional CMC fabricationtechniques.

With its heat resistance and reduced cracking, the composite material orthe ceramic material (e.g., CMC) formed from the preceramic resinformulation and carbon fibers may be used in a variety of articles, suchas in aerospace or other industries. The composite material or theceramic material according to embodiments of the disclosure may be usedto form components of rocket motors or other aerostructures. Thecomposite material or the ceramic material according to embodiments ofthe disclosure may be used as a structural component of a rocket motoror of a high temperature aerostructure. The composite material or theceramic material may be used as a component of a nozzle of the rocketmotor or of a casing of the rocket motor. The aerostructure may include,but is not limited to, a turbine, a turbine blade, a turbine housing, aturbine engine vane, an insulating tile, a rotor blade, an insulationblanket, a compressor blade, a wing component, a fuselage skin, alanding gear, an exhaust nozzle, an engine exhaust duct, a nose cone, are-entry shield, or a heat shield. In addition to structural components,the composite material or the ceramic material may be used as anoxidative resistant coating on a rocket motor nozzle or other hightemperature aerostructure, a high temperature adhesive, a mortarmaterial for filling cracks or gaps, an insulation, a thermal protectionmaterial, or a thermal ablation material. The composite material or theceramic material according to embodiments of the disclosure may also beused as a bonding material between other components, such as betweenother components of a rocket motor or other components of anaerostructure. The composite material or the ceramic material may,therefore, be part of a laminate structure that includes aerostructurecomponents or rocket motor components.

The composite material or CMC according to embodiments of the disclosuremay be formulated for applications having a short functional life, suchas less than about 30 minutes. By way of example only, the compositematerial or the CMC may be used as a component of a rocket motor nozzle,which is expected to function for less than about 30 minutes during useand operation. In a rocket motor nozzle, the composite material may beceramified in situ, such as by curing the composite material asdescribed above and then ceramifying the composite material during useand operation of the rocket motor. By changing the fibers, the compositematerial or CMC may be prepared for applications having a longfunctional life, such as greater than about 1,000 hours or greater thanabout 10,000 hours. By way of example only, the CMC may be configured asa turbine component.

FIG. 1 is a simplified cross-sectional view of a rocket motor 1000(e.g., a solid rocket motor), in accordance with embodiments of thedisclosure. The rocket motor 1000 may, for example, be configured to bea component (e.g., stage) of a larger assembly (e.g., a multi-stagerocket motor assembly). As shown in FIG. 1, the rocket motor 1000includes a casing 1002, a propellant structure 1004 disposed within thecasing 1002, and a nozzle assembly 1006 connected to an aft end of thecasing 1002. The rocket motor 1000 may also include one or more of aliner structure 1008 and an insulation structure 1010 between thepropellant structure 1004 and the casing 1002. For example, the linerstructure 1008 may be located on or over the propellant structure 1004,and the insulation structure 1010 may be located on and between theliner structure 1008 and an inner surface of the casing 1002. Thecomponents of the rocket motor 1000 may be formed using conventionalprocesses and equipment, which are not described in detail herein. Thecomposite material or ceramic material according to embodiments of thedisclosure may be used in one or more components of the rocket motor1000. By way of example only, at least a portion of the nozzle assembly1006 or the casing 1002 may be formed of the ceramic material accordingto embodiments of the disclosure.

While embodiments described herein refer to preceramic precursors ofsilicon carbide and silicon dioxide, the preceramic precursor of silicondioxide may also be used with preceramic precursors of other ceramics,such as preceramic precursors of silicon carbide, preceramic precursorsof silicon nitride, preceramic precursors of silicon hexaboride,preceramic precursors of aluminum nitride, preceramic precursors ofboron nitride, preceramic precursors of boron carbide, preceramicprecursors of titanium boride, preceramic precursors of titaniumcarbide, and preceramic precursors of hafnium carbide.

The following examples serve to explain embodiments of the disclosure inmore detail. These examples are not to be construed as being exhaustiveor exclusive as to the scope of this disclosure.

EXAMPLES Example 1 Precursor Resin Formulation

A preceramic resin formulation including 100 parts of a polycarbosilanepreceramic polymer commercially available from EEMS, LLC as CSO-110, 25parts of a organically modified silicon dioxide preceramic polymercommercially available from Gelest, Inc. as VQM-146, and 1 part of aplatinum catalyst commercially available from EEMS as CLC-PL005 wasprepared. The CSO-110, VQM-146, and platinum catalyst were combined toproduce the preceramic resin formulation including 80 wt % CSO-110 and20 wt % of the VQM-146. A control formulation including only CSO-110 wasalso produced.

The preceramic resin formulation and the control formulation wereexposed to 121° C. (250° F.) for 4 hours to cure the preceramic resinformulation and the control formulation, and then ceramified at atemperature of about 900° C. for 2 hours to produce the respectiveceramic materials. A post-cure after the 121° C. (250° F.) cure wasperformed at 370° C. (700° F.) for an additional 4 hours.

Example 2 Ceramic Yield and Mechanical Integrity

Thermogravimetric analysis (TGA) of the ceramic material formed from thepreceramic resin formulation of Example 1 and the ceramified controlformulation was conducted to determine the weight loss of the ceramicmaterials as a function of temperature. The TGA was conducted byconventional techniques. As shown in FIG. 2, the ceramic material formedfrom the preceramic resin formulation of Example 1 exhibited a 78.4%ceramic yield, while the ceramic material formed from the controlformulation exhibited a 64.6% ceramic yield. Therefore, the ceramicmaterial formed from the preceramic resin formulation of Example 1 had a21.4% increase in mass retention compared to the ceramified controlformulation including only the CSO-110. Thus, the ceramic yield of theceramic material formed from the preceramic resin formulation of Example1 was significantly increased compared to the ceramified controlformulation.

In addition to the increased ceramic yield, no cracking was observedwith the cured preceramic resin formulation (cured at 250° F. for 4hours) of Example 1, as shown in FIG. 3. The cured preceramic resinformulation formed from the polycarbosilane preceramic polymer and theorganically modified silicon dioxide preceramic polymer exhibited netshape curing with no cracking. In contrast, the cured controlformulation (cured at 250° F. for 4 hours) exhibited extensive cracking.

Example 3 Precursor Resin Formulations

Preceramic resin formulations including 100 parts of the polycarbosilanepreceramic polymer CSO-110, 25 parts of the organically modified silicondioxide preceramic polymer VQM-146, and 1 part of the platinum catalystCLC-PL005 were prepared. The preceramic resin formulations also includedtitanium diboride and boron nitride (24:1 of titanium diboride:boronnitride, referred to herein as HTR42), zirconium dioxide and titaniumdiboride (2:1 zirconium dioxide:titanium diboride, referred to herein asHTR44), or titanium diboride, zirconium dioxide, and boron nitride(21:15:1 titanium diboride:zirconium dioxide:boron nitride, referred toherein as HTR45). The zirconium dioxide had an average mean diameter of0.6 μm and was commercially available from Momentive PerformanceMaterials Inc. (Waterford, N.Y.) as HCTF. The titanium diboride had anaverage mean diameter of 3 μm and was commercially available fromPanadyne Inc. (Montgomeryville, Pa.) as PGZ-06. The zirconium dioxideand titanium diboride were present at 65 wt % with respect to the resin.The CSO-110, VQM-146, platinum catalyst, zirconium dioxide, and titaniumdiboride were combined with mixing.

Example 4 CMC Test Specimens-Shrinkage and Mass Loss

Test specimens were produced by impregnating HExTow® IMT-R-12K fibers(PAN fibers) and YSH60A-A2S-12K graphite fibers (pitch fibers) with thepreceramic resin formulations described in Example 3. The impregnatedfibers were continuously wound on a mandrel, cured at 121° C. (250° F.)for four hours, subjected to a post-cure at 371° C. (700° F.) for twohours, and exposed to 1,093° C. (2,000° F.) for 30 minutes for theceramic conversion to form ring-shaped test specimens. The curing andceramification were conducted in an inert atmosphere (less than about100 ppm oxygen). The density of the test specimen formed from HTR42 was2.22 g/cm³, the density of the test specimen formed from HTR44 was 2.19g/cm³, and the density of the test specimen formed from HTR45 was 2.07g/cm³.

Dimensions of the test specimen having HTR42 as the preceramic resinformulation were measured after the 371° C. (700° F.) post-cure andafter the 1,093° C. (2,000° F.) ceramic conversion. The test specimenhad low change in dimensions (ring width, ring thickness, ring innerdiameter (ID), as shown in FIG. 4.

Mass loss of the test specimens having HTR42, HTR44, or HTR45 as thepreceramic resin formulation were measured after 371° C. (700° F.)post-cure and after the 1,093° C. (2,000° F.) ceramic conversion. Thetest specimens had low mass loss, as shown in FIG. 5.

Example 5 Test Specimens-Mechanical Properties

The preceramic resin formulation described in Example 3 as HTR42 wasimpregnated into HExTow® IMT-R-12K fibers (PAN fibers). The PAN fiberswere coated with four different sizing compositions. The impregnatedfibers were continuously wound on a mandrel, cured at 121° C. (250° F.)for four hours, and subjected to a post-cure at 204° C. (400° F.) fortwo hours to form ring-shaped test specimens. Tensile properties of thefour test specimens were measured by conventional techniques. The testspecimens are referred to as CMC-1, CMC-2, CMC-3, and CMC-4 and differin the coating on the PAN fibers. As shown in FIGS. 6 and 7, the testspecimens exhibited low percentages of elongation at failure and goodtensile strength.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, the disclosure is not intended to be limited to the particularforms disclosed. Rather, the disclosure encompasses all modifications,equivalents, and alternatives falling within the scope of the disclosureas defined by the following appended claims and their legal equivalents.

What is claimed is:
 1. Impregnated fibers comprising fibers and apreceramic resin formulation comprising a polycarbosilane preceramicpolymer, an organically modified silicon dioxide preceramic polymer, andat least one filler, the at least one filler comprising first particleshaving an average mean diameter of less than about 1.0 μm and secondparticles having an average mean diameter of from about 1.5 μm to about5 μm.
 2. The impregnated fibers of claim 1, wherein the fibers comprisepolyacrylonitrile-based fibers.
 3. The impregnated fibers of claim 1,wherein the fibers comprise pitch-based fibers.
 4. A composite materialcomprising fibers and a reaction product of a polycarbosilane preceramicpolymer, an organically modified silicon dioxide preceramic polymer, andat least one filler, the at least one filler comprising first particleshaving an average mean diameter of less than about 1.0 μm and secondparticles having an average mean diameter of from about 1.5 μm to about5 μm.
 5. The composite material of claim 4, wherein the compositematerial is configured as at least a portion of a rocket motor nozzle ora rocket motor casing.
 6. The composite material of claim 4, wherein thecomposite material is configured as at least a portion of a turbine, aturbine blade, a turbine housing, a turbine engine vane, an insulatingtile, a rotor blade, an insulation blanket, a compressor blade, a wingcomponent, a fuselage skin, a landing gear, an exhaust nozzle, an engineexhaust duct, a nose cone, a re-entry shield, or a heat shield.
 7. Thecomposite material of claim 4, wherein the composite material comprisesan oxidative resistant coating on a rocket motor nozzle or other hightemperature aerostructure, a high temperature adhesive, a mortarmaterial, an insulation, a thermal protection material, a thermalablation material, or a matrix material of a ceramic matrix composite.8. A method of forming a ceramic matrix composite, comprising: passingfibers through a preceramic resin formulation comprising apolycarbosilane preceramic polymer and an organically modified silicondioxide preceramic polymer; impregnating the fibers with the preceramicresin formulation; and forming the impregnated fibers into a compositematerial.
 9. The method of claim 8, wherein passing fibers through apreceramic resin formulation comprises passing the fibers through apreceramic resin formulation formulated to exhibit a viscosity of fromabout 200 cP at about 25° C. to about 5,000 cP at a temperature of about25° C.
 10. The method of claim 8, wherein passing fibers through apreceramic resin formulation comprises forming continuous fibersimpregnated with the preceramic resin formulation.
 11. The method ofclaim 8, wherein passing fibers through a preceramic resin formulationcomprises passing the fibers through a bath containing the preceramicresin formulation.
 12. The method of claim 8, wherein passing fibersthrough a preceramic resin formulation comprises passing carbon fibersthrough the preceramic resin formulation.
 13. The method of claim 8,wherein passing fibers through a preceramic resin formulation comprisespassing the fibers through a preceramic resin formulation comprising thepolycarbosilane preceramic polymer, the organically modified silicondioxide preceramic polymer, and at least one filler comprising firstparticles having an average mean diameter of less than about 1.0 μm andsecond particles having an average mean diameter of from about 1.5 μm toabout 5 μm.
 14. The method of claim 13, wherein passing fibers through apreceramic resin formulation comprises passing the fibers through thepreceramic resin formulation comprising the polycarbosilane preceramicpolymer, the organically modified silicon dioxide preceramic polymer,and at least one of zirconium dioxide or titanium diboride.
 15. Themethod of claim 13, wherein passing fibers through a preceramic resinformulation comprises passing the fibers through the preceramic resinformulation comprising the polycarbosilane preceramic polymer, theorganically modified silicon dioxide preceramic polymer, zirconiumdioxide, and titanium diboride.
 16. The method of claim 8, whereinforming the impregnated fibers into a composite material comprisesforming the composite material at a net shape.
 17. The method of claim8, wherein forming the impregnated fibers into a composite materialcomprises forming the composite material at a near-net shape.
 18. Themethod of claim 8, wherein forming the impregnated fibers into acomposite material comprises curing the impregnated fibers at atemperature of from about 121° C. to about 371° C. to form the compositematerial and ceramifying the composite material at a temperature ofgreater than about 816° C.
 19. The method of claim 8, wherein curing theimpregnated fibers comprises curing the impregnated fibers at atemperature of about 371° C. and ceramifying the composite material at atemperature of about 1,093° C.
 20. The method of claim 8, whereinforming the impregnated fibers into a composite material comprisesforming the composite material at a ceramic yield of greater than about90%.
 21. The method of claim 8, wherein forming the impregnated fibersinto a composite material comprises forming the composite material at amass loss of less than about 10%.
 22. The method of claim 8, furthercomprising machining the composite material.
 23. The method of claim 8,further comprising ceramifying the composite material to form a ceramicmatrix composite.
 24. The method of claim 23, wherein forming theimpregnated fibers into a composite material comprises curing theimpregnated fibers and ceramifying the composite material at a singleheat treatment at a temperature of about 1,200° C.